Refrigeration apparatus and method



June 1966 L. H. LEONARD, JR 3,

REFRIGERATION APPARATUS AND METHOD Filed July 28, 1964 IN VEN TOR.

L n'uls H. LEUNARQJR.

ATTDENEY United States Patent 3 257,817 REFRIGERATION AfPARATUS AND METHOD Louis H. Leonard, Jn, De Witt, N.Y., assignor to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed July 28, 1964, Ser. No. 385,563 6 Claims. (Cl. 62-98) This invention relates to refrigeration and, more particularly, to a system and method for providing refrigera tion wherein a chilled watertube bundle is flooded with a cooling liquid and a volatile refrigerant is passed through the liquid for directly cooling the liquid and thereby indirectly cooling chilled water passing through the bundle.

, The cooling liquid may be circulated, as in a percolating manner, about the bundle to improve cooling of the chilled water in the bundle. When only low cooling capacity is required and condensing water is below a desired leaving chilled water temperature, vapor is released by the refrigerant upon cooling the chilled water bundle and is circulated by a process of natural convection with the compressor inoperative, thus providing free cooling.

Various types of refrigeration systems incorporating flooded evaporators are known in the art. It is common practice to flood a chilled water tube bundle in an evapo rator with boiling refrigerant which vaporizes to cool the bundle and the chilled Water therein. Systems using such evaporators require a relatively large quantity of refrigerant in order to suitably flood the bundle, thus increasing the overall cost of the system. A disadvantage of many flooded type evaporators is that at low cooling capacity operation, the bundle is often only slightly immersed in liquid refrigerant, resulting in poor operation and efficiency. Also, tube bundles submerged in pure refrigerant are more susceptible to tube freeze-up since the chilled water passing through the tube bundle may freeze and burst the tubes. Furthermore, most refrigerants react unfavorably with materials, such as aluminum, which might otherwise be advantageously used in refrigeration machines.

It is a primary object of this invention to provide a new and improved refrigeration system and method of providing refrigeration.

Another object is to provide a new and improved flooded type evaporator for use in a refrigeration system.

Still another object is to provide a new and improved evaporator including a chilled water tube bundle, the evaporator having provision for holding cooling water and substantially submerging the bundle in the water, with provision for passing refrigerant into the cooling water to cool the cooling water and thereby to cool the chilled water in the bundle. A related object is rovision in such an evaporator of an aluminum tube bundle.

Another object is to provide a new and improved refrigeration system of the flooded evaporator type in which the evaporator has a chilled Water tube bundle and provision for submerging the bundle in cooling water and including provision for cooling and agitating the cooling water by vaporizing the refrigerant and the system providing free cooling of the chilled water bundle at low cooling capacity when the condensing water temperature is lower than the desired leaving chilled water temperature.

Still another object is provision in a refrigeration system having an evaporator including a chilled water tube bundle, of a new and improved method of providing refrigeration including the steps of flooding the bundle with cooling water, and passing refrigerant into direct contact with the cooling water to cool the chilled water in the tube bundle.

These and other objects of the invention will be apparice ent from the following description and the accompanying drawing which is a fragmentary diagrammatic view of refrigeration apparatus incorporating the invention.

The invention will be described with reference to water (the cooling water) which is a preferred liquid for flooding a chilled Water tube bundle, and a referred refrigerant which is octafluorocyclobutane, commonly referred to as C318 and having a chemical formula C F for direct contact with the cooling water to cool this water and thereby the chilled water in the bundle. These fluids are particularly preferred because of their relative immiscibility and because they are inherently highly stable and, as utilized in the system, do not tend to decompose or chemically react with each other or other materials in the system or cause or promote corrosion or undesirable by-products. Also, this refrigerant is a relatively nncondensible vapor at the temperature and pressure at which water condenses as well as at the usual ambient atmospheric conditions of temperature and pressure. However, the other fluids having the desired chemical and physical properties, such as ethylene glycol which may be used in place of water, as well as other refrigerants, may be utilized within the scope of this invention.

Referring to the drawing, a refrigerant compressor 11 may be driven in any suitable manner, for example by a shaft 11 connected with a steam turbine which is not shown, to pass compressed refrigerant vapor through a line 12 to a refrigerant condenser 13. A condensing water inlet line 14 passes tower or condensing water through a condensing bundle 15 the refrigerant condenser from which the condensing water is discharged through a condensing water discharge line 16 for return to the tower. From the refrigerant condenser 13, liquid refrigerant condensate flows through a condensate line 17 to an evaporator 18. A suitable pressure seal and refrigerant flow restricting means, such as a float valve 18' is provided in the line 17.

The evaporator 18 is of the flooded tube type and may be of any suitable shape. Herein, the evaporator has generally a cylindrical shell 18 and its longitudinal axis is generally horizontal. A chilled water tube bundle 19 is positioned in a lower portion of the shell 18" and is suitably connected with a returning chilled water line 20 and a leaving chilled water line 21. As illustrated, the bundle 19 is at all times, including at low cooling capacity, fully submerged in cooling water 22 in the lower portion of the evaporator shell. The refrigerant condensate line 17 opens through an inlet 23 in the shell 18" and communicates with suitable refrigerant distributing means 24 preferably extending longitudinally along substantially the entire length of the bottom of the shell for passing liquid refrigerant into direct contact with the cooling water 22. As the liquid refrigerant passes into the water, it vaporizes and causes substantial agitation of the water while cooling the water and passing from the water into an upper portion of the evaporator shell from which it is withdrawn through a refrigerant vapor outlet 25 communicating with a suction line 26 to the refrigerant compressor 11. A suitable eliminator, as 27, may be provided in association with the refrigerant vapor outlet 25 for effectively preventing withdrawal of droplets of water from the evaporator 18.

Suitable baffles, as 28, preferably parallel baffles, generally vertically disposed and extending longitudinally substantially the entire length of the evaporator shell 18" and spaced from the shell and the refrigerant distributing means 24, provide circulation of the water 22 in a predetermined path within the shell and effectively prevent the refrigerant vapor from passing along the lower portion of the evaporator shell and skirting the water 22. Thus, as the liquid refrigerant enters the evaporator, it vaporizes and causes the water 22 to move upwardly in the center of the shell and then (as indicated by the arrows) over the tops of the baflies, which are below the water level. The water then circulates downwardly between the ballie and the adjacent portion of the shell to provide a percolating action as the water circulates under the lower edge of the baffle which is vertically spaced from the shell.

By way of specific example, with an entering chilled water temperature of 54 F. and a leaving chilled water temperature of 44 F. liquid refrigerant at a temperature of 36 F. may enter into direct contact with the water in the evaporator shell at a temperature of 38 F. and a suction pressure of 21 p.s.i.a.

Particularly in air conditioning systems, very little cooling may be required at certain times. When the condensing water temperature entering the refrigerant condenser through the inlet line 14 is below the desired chilled water temperature leaving through the chilled water line 21, the compresser 11 may be stopped and the refrigerant circulated through the evaporator by a process of natural convection, thus providing free cooling. More particularly, refrigerant 'vapor passes from the evaporator 18 through the suction line 26 and the inoperative compressor 11 into the cool and relatively low pressure refrigerant condenser 13 where it condenses upon being cooled by the condensing water bundle 15. From the refrigerant condenser, the liquid refrigerant drains through the condensate line 17 and back into the evaporator and vaporizes through the water 22 thus cooling the chilled water within the bundle 19 and providing free cooling to the load to be cooled.

The present system is particularly useful for free cooling in that the chilled water tube bundle 19 is always fully submerged in the intermediate cooling water 22 and no special provision need be made for effectively completely flooding the chilled water bundle.

Due to a malfunction of controls, for example, suction temperature in the evaporator could drop below 32 F., resulting in chilled water freeze-up and-tube breaking on conventional evaporators. With the present evaporator design, the cooling water 2-2 will freeze before the chilled water in the tube bundle '19, and the resultant ice serves to stop the flow of refrigerant throughout the evaporator before the chilled water in the bundle freezes. For freezeproof, outdoor installations, or low temperature brine cooling applications, ethylene glycol can be used in place of cooling water 22 as the intermediate heat transfer medium, since it is completely stable in the presence of C318, as previously mentioned.

The invention allows the use of an absolute minimum of refrigerant charge. Even with high cost refrigerants, due to the low quantity required because of the cooling water, rather than refrigerant, flooding the chilled water tube bundle, the actual refrigerant cost may be less than for the refrigerant charge in a conventional system. Due to the pressure-temperature relationship of C318, the evaporator and condenser are always above atmospheric pressure and the usual purge system is not required. By using a mixture of water and C318, aluminum evaporator tubes are commercially practical and cost estimates indicate a substantial saving in the use of such tubes. recirculating pump or spray header is required. Nor is there need for any type of moisture indicator, and small amounts of condensing or chilled water leakage through leaking tube joints will not cause corrosion problems as with many refrigeration machines. Furthermore, the invention permits the manufacture of a truly hermetic machine, that is a machine which is entirely air tight.

It should further be noted that the tube bundle remains submerged at all times, even under extremely low partial load operation. This results in greatly improved partial load operation. With conventional flooded evaporators,

the entire tube surface is effective only at full load, when full boiling is achieved.

While a preferred embodiment of the invention has been described and illustrated, it will be understood that the invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

I claim:

1. For use in a refrigeration system of the flooded evaporator type, the combination comprising, an evaporator shell having a lower portion for holding water, a chilled water tube bundle in said lower portion of said shell to be substantially fully submerged in said water, means for cooling and agitating said water to cool said tube bundle and including means defining an inlet gencrally centered at the bottom of said shell for the passage of liquid refrigerant upwardly through said water, means responsive to said refrigerant passing from said inlet into direct contact with said water for circulating said water in a percolating manner upwardly from said inlet with said refrigerant and then downwardly along said shell toward said inlet and including upwardly extending baffle means spaced from said shell and said inlet, and means for withdrawing refrigerant vapor from an upper portion of said shell, whereby the water flooding the tube bundle reduces the quantity of refrigerant charge required in the system over that which would be required if the bundle were flooded with only refrigerant, and the bundle is enveloped in water to effectively prevent contact between the refrigerant and the bundle.

2. The combination of claim 1 in which said tube bundle :has aluminum tubes to be submerged in said water, and the means for the passage of liquid refrigerant passes refrigerant C318.

3. vIn a combination of claim 1 in which said evaporator shell is generally cylindrical with its longitudinal axis generally horizontally disposed, and the inlet and the baifle means extend substantially the length of said shell in the direction of said axis.

4. A method of operating a refrigeration system having an evaporator shell and centrally located therein a chilled water tube bundle, comprising the steps of flooding said bundle with abody of water, passing liquid refrigerant through a central portion of the body of water to cool the bundle and circulate said portion of the water in generally the same direction as the refrigerant passing thcrethrough and thereafter downwardly along said shell by vaporizing the refrigerant, and withdrawing the refrigerant vapor from the evaporator.

5. The method of claim 4 in which said water is circulated in a percolating manner within the evaporator.

6. The method of claim 4 in which the system includes a refrigerant condenser for receiving condensing water to condense the refrigerant vapor, and in which said refrigerant is circulated by natural convection to provide free cooling when the condensing water is below the desired temperature of chilled Water leaving said bundle.

References Cited by the Examiner UNITED STATES PATENTS 310,025 12/1884 Brewer 62121 1,692,223 11/1928 Pinkerton et al. 62339 1,981,598 11/19 4 King 62394 X 2,049,155 7/1936 Coleman 62393 X 2,114,12'8 4/1938 Smith 62--502 2,191,623 2/1940 Philipp 62-393 X 2,440,930 5/1948 Camilli et al. 62502 X 2,821,844 2/1958 Olson 62-393 X ROBERT A. OLEARY, Primary Examiner.

MEY'ER PERLIN, Examiner.

LLOYD L. KING, Assistant Examiner. 

4. A MEHTOD OF OPERATING A REFRIGERATION SYSTEM HAVING AN EVAPORATOR SHELL AND CENTRALLY LOCATED THEREIN A CHILLED WATER TUBE BUNDLE, COMPRISING THE STEPS OF FLOODING SAID BUNDLE WITH A BODY OF WATER,PASSING LIQUID REFRIGERANT THROUGH A CENTRAL PORTION OF THE BODY OF WATER TO COOL THE BUNDLE AND CIRCULATE SAID PORTION OF THE WATER IN GENERALLY THE SAME DIRECTION AS THE REFRIGERNAT PASSING THERETHROUGH AND THEREAFTER DOWNWARDLY ALONG SAID SHELL BY VAPORIZING THE REFRIGERANT, AND WITHDRAWING THE REFRIGERANT VAPOR FROM THE EVAPORATOR. 